Direct observation of bond formations

February　19, 2015

High Energy Accelerator Research Organization, KEK
Institute for Basic Science, IBS
Korea Advanced Institute of Science and Technology, KAIST
RIKEN
Japan Synchrotron Radiation Research Institute, JASRI

A collaboration between researchers from KEK, the Institute for Basic Science (IBS), the Korea Advanced Institute of Science and Technology (KAIST), RIKEN, and the Japan Synchrotron Radiation Research Institute (JASRI) used the SACLA X-ray free electron laser (XFEL) facility for a real time visualization of the birth of a molecular that occurs via photoinduced formation of a chemical bonds. This achievement was published in the online version of the scientific journal "Nature" (published on 19 February 2015).

Direct "observation" of the bond making, through a chemical reaction, has been longstanding dream for chemists. However, the distance between atoms is very small, at about 100 picometer, and the bonding is completed very quickly, taking less than one picosecond (ps). Hence, previously, one could only imagine the bond formation between atoms while looking at the chemical reaction progressing in the test-tube.

In this study, the research group focused on the process of photoinduced bond formation between gold (Au) ions dissolved in water(Fig. 1). In the ground state (S₀ state in Fig. 2) Au ions that are weakly bound to each other by an electron affinity and aligned in a bent geometry. Upon a photoexcitation, the S₀ state rapidly converts into an excited (S₁ state in Fig. 2) state where Au-Au covalent bonds are formed among Au ions aligned in a linear geometry. Subsequently, the S₁ state transforms to a triplet state (T₁ state in Fig. 2) in 1.6 ps while accompanying further contraction of Au-Au bonds by 0.1 Å. Later, the T₁ state of the trimer converts to a tetramer (tetramer state in Fig. 2) on nanosecond time scale. Finally, the Au ions returned to their original loosely interacting bent structure.

In this research, the direct observation of a very fast chemical reaction, induced by the photo-excitation, was succeeded (Fig. 2, 3). Therefore, this method is expected to be a fundamental technology for understanding the light energy conversion reaction. The research group is actively working to apply this method to the development of viable renewable energy resources, such as a photocatalysts for artificial photosynthesis using sunlight.

This research was supported by the X-ray Free Electron Laser Priority Strategy Program of the MEXT, PRESTO of theJST, and the the Innovative Areas "Artificial Photosynthesis (AnApple)" grant from the Japan Society for the Promotion of Science (JSPS).

Fig. 2. Observed changes in the molecular structure of the gold complex

Fig. 3. Schematic view of the research of photo-chemical reactions by the molecular movie

Media Contact

[ for research ]

Prof. Shin-ichi Adachi
Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Japan

[ for public relations ]

Saeko Okada
Public Relations Office, High Energy Accelerator Research Organization (KEK), Japan
TEL: +81-29-879-6047
FAX: +81-29-879-6049
E-mail: press@kek.jp

Yoon, Hyang Lan
KAIST Public Relations Division, Korea Advanced Institute of Science and Technology (KAIST), Korea
E-mail: hlyoon@kaist.ac.kr

Kim, Seonhea Sunny
Department of Communications, Institute for Basic Science (IBS), Korea
Email: sunnykim@ibs.re.kr

Public Relations Office, RIKEN, Japan
TEL: +81-48-467-9272
FAX: +81-48-462-4715
E-mail: ex-press@riken.jp

Related Link

Institute of Materials Structure Science,IMSS
Institute for Basic Science,IBS
Korea Advanced Institute of Science and Technology, KAIST
RIKEN
Japan Synchrotron Radiation Research Institute, JASRI
Photon Factory
SACLA

Related Issue

June 17, 2012　Press Release
Visualizing a photosensitizer complex in action